[PATCH] PR lto/94249: Correct endianness detection with the __BYTE_ORDER macro

[Maciej W. Rozycki]

Correct an issue with GCC commit 906b3eb9df6c ("Improve endianess 
detection.") and fix a typo in the __BYTE_ORDER fallback macro check 
that causes compilation errors like:

.../include/plugin-api.h:162:2: error: #error "Could not detect architecture endianess"

on systems that do not provide the __BYTE_ORDER__ macro.

	include/
	PR lto/94249
	* plugin-api.h: Fix a typo in the __BYTE_ORDER macro check.
---
On Tue, 24 Mar 2020, Martin Liška wrote:

> >> +/* Detect endianess based on _BYTE_ORDER.  */
> >> +#if _BYTE_ORDER == _LITTLE_ENDIAN
> > 
> > So most likely _BYTE_ORDER and _LITTLE_ENDIAN macros will not be defined.
> > Which means this will be handled as #if 0 == 0 and override the
> >> +#define PLUGIN_LITTLE_ENDIAN 1
> > 
> > will define also PLUGIN_LITTLE_ENDIAN.
> 
> Ok, for being sure, I've wrapped all equality comparison with corresponding
> check of the LHS is defined.

 This change, when merged into binutils, caused BFD to fail building in 
one of my configurations:

In file included from .../bfd/elflink.c:31:
.../bfd/../include/plugin-api.h:162:2: error: #error "Could not detect architecture endianess"
make[4]: *** [elflink.lo] Error 1

This is due to a missing underscore in the:

#ifdef _BYTE_ORDER

check.

 OK to apply this hopefully obvious fix to GCC and then merge to binutils?

 NB if posting as an attachment please try matching the message subject 
with the change heading as otherwise it takes a lot of effort to track the 
patch submission corresponding to a given commit.

  Maciej
---
 include/plugin-api.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

binutils-include-plugin-api-byte-order.diff
Index: binutils/include/plugin-api.h
===================================================================
--- binutils.orig/include/plugin-api.h
+++ binutils/include/plugin-api.h
@@ -51,7 +51,7 @@
 /* Older GCC releases (<4.6.0) can make detection from glibc macros.  */
 #if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID__)
 #include <endian.h>
-#ifdef _BYTE_ORDER
+#ifdef __BYTE_ORDER
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 #define PLUGIN_LITTLE_ENDIAN 1
 #elif __BYTE_ORDER == __BIG_ENDIAN